Stephanomeria occultata , a new diploid (2n = 16) species of wirelettuce endemic to the Weber River drainage of northern Utah, is herein described, and a key to all perennial members of the genus is provided. The populations of S. occultata occur in unstable gravelly slopes in close proximity to the Weber River between 590–1650min elevation. Stephanomeria occultata is characterized from other species in the region by its large growth habit, which is up to 1mtall, numerous stems, well-developed tomentose leaves, and large number of ray florets (8–14). Information on habitat, ecology, distribution, taxonomic relationships, conservation, as well as maps, photographs, and illustrations are provided. The two populations of S. occultata may contain as few as 200 genets with up to 500 ramets and these small populations are vulnerable to encroaching weeds and anthropogenic disturbance.